Signal transmission circuit

ABSTRACT

The signal transmission circuit is provided, said signal transmission circuit being capable of stable operations even with a source power of low voltage and a fast operation. The signal transmission circuit comprises plural stages of circuit in each of which the pulse voltage according to the driving pulse is sequentially outputted. The circuit of each stage includes: the output transistor T 12  for outputting the pulse voltage to the source, according to the driving pulse; the bootstrap capacitor C 1  connected between the gate and the source of the output transistor; the first charging transistor T 11  for charging the bootstrap capacitor; the first and the second discharging transistor T 13  and T 14  for discharging the electric charge of the bootstrap capacitor; and the logical circuit which (i) turns on the first and the second discharging transistor, according to the driving pulse for each circuit of the other stages, and (ii) turns off the first and the second discharging transistor, according to the gate signal of the charging transistor.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a signal transmission circuit,so-called shift register, in particular, to the shift register fordriving Liquid Crystal Display (LCD) and Metal Oxide Semiconductor (MOS)image sensor.

(2) Description of the Related Art

FIG. 1 is a circuit diagram showing a structure example of aconventional signal transmission circuit, and describes the four stagesof the circuit comprising multiple stages (refer to Japanese Patentpublication No. H3-75960 (FIG. 3)). This signal transmission circuitcomprises the output transistor to the next stage T12, T22, T32 and T42,the bootstrap capacitor C1, C2, C3 and C4, the bootstrap capacitorcharging transistor T11, T21, T31 and T41, the first dischargingtransistor T13, T23, T33 and T43 and the second discharging transistorT14, T24, T34 and T44.

Each element of this signal transmission circuit is provided with, atleast, one or more than one of the source voltage VDD, the drivingpulses V1 and V2 and the start pulse VST.

The operations performed by the conventional signal transmission circuitof such structure as described above will be explained as following.When the start pulse VST rises to the logical “High” level, thebootstrap capacitor charging transistor T11 of the first stage turns on.Thus, the electric charge is charged in the bootstrap capacitor C1 untilthe electric voltage becomes (the source voltage VDD—the thresholdvoltage Vt1 of the transistor T 11).

When the charging voltage of the bootstrap capacitor C1 exceeds thethreshold voltage of the output transistor T12, the output transistorT12 of the first stage turns on. Then, after the driving pulse V1 of thelogical “High” level is inputted into the drain of the output transistorT12, the voltage of the driving pulse V1 and the potential differencebetween the both ends of the bootstrap capacitor C1 are added andapplied to the gate of the output transistor T12. When the gatepotential (the node N11) of the output transistor T12 rises higher thanthe potential of the driving pulse V1, the driving pulse V1 getsoutputted as the output pulse OUT1 from the node N12.

At the same time, when (i) the voltage of the node N12 is applied to thegate of the bootstrap capacitor charging transistor T21 of the secondstage, (ii) the transistor T21 turns on, and (iii) the bootstrapcapacitor C2 is charged to the source voltage VDD while the chargingvoltage does not fall for the threshold voltage Vt2 of the transistorT21.

When the charging voltage of the bootstrap capacitor C2 exceeds thethreshold voltage of the output transistor T22, the output transistorT22 of the second stage turns on. Then, after the driving pulse V2 ofthe logical “High” level is inputted into the drain of the outputtransistor T22, the potential of the driving pulse V2 and the potentialdifference between the both ends of the bootstrap capacitor C2 are addedand applied to the gate of the output transistor. When the gate voltage(the node N21) of the transistor T22 rises higher than the potential ofthe driving pulse V2, the driving pulse V2 is outputted as the outputpulse OUT2 from the node N22.

At the same time, when the voltage of the node N22 is applied to thegate of the bootstrap capacitor charging transistor T31 of the thirdstage, the transistor T31 turns on. Thus, the bootstrap capacitor C3 ischarged to the source voltage VDD without falling for the thresholdvoltage Vt3 of the transistor T32.

When the charging voltage of the bootstrap capacitor C3 exceeds thethreshold voltage of the output transistor T32, the output transistorT32 of the third stage turns on.

Such operations as described above are repeated, and the signaltransmission circuit further sequentially outputs the output pulse Out3and Out4.

FIG. 2 is a circuit diagram showing a structure example of aconventional error operation preventative signal transmission circuit.In this improved signal transmission circuit, the source voltage iscertainly applied to the gate of the bootstrap capacitor chargingtransistor, while in the conventional signal transmission circuit shownin FIG. 1, only the lower voltage than the source voltage VDD wasapplied to the gate of the bootstrap capacitor charging transistor. Thiserror operation preventative signal transmission circuit prevents (i)the voltages of the nodes N11, N21, N31 and N41 from gradually fallingand (ii) the output pulses from stopping at several stages forward.

The error operation preventative signal transmission circuit shown inFIG. 2 is different from the signal transmission circuit shown in FIG.1, and it further comprises the first error operation preventativetransistor T35 and T45, respectively for the circuit of the third andthe fourth stages. As for the transistor T35, (i) the gate is connectedto the source (the node N12) of the output transistor T12, (ii) thedrain is connected to the source (the node N31) of the bootstrapcapacitor charging transistor T31, and (iii) the source is earthed. Asfor the transistor T45, (i) the gate is connected to the source (thenode N22) of the output transistor T22, (ii) the drain is connected tothe source (the node N41) of the bootstrap capacitor charging transistorT41, and (iii) the source is earthed.

In addition, the error operation preventative signal transmissioncircuit shown in FIG. 2 is different from the signal transmissioncircuit shown in FIG. 1 in that the gate of the second dischargingtransistor of each stage is connected to the source of the outputtransistor of the next stage. For example, the gate of the seconddischarging transistor T14 of the first stage is connected to the sourceof the output transistor T22 of the second stage.

The operations performed by the error operation preventative signaltransmission circuit will be explained as following.

FIG. 3 is a time chart showing the pulse voltage of each unit in theconventional signal transmission circuit using only NMOS. This circuitis a 3V type circuit, wherein the voltage amplitude of the drivingpulses V1 and V2 and the source voltage VDD are 3V.

However, the voltage amplitude of the start pulse VST is 5V. Here, thereason why only the source voltage of the start pulse VST is 5V isbecause only in the bootstrap capacitor charging transistor T11 of thefirst stage where the start pulse VST is inputted, the high voltage fromthe previous stage cannot be provided. Therefore, only the start pulseVST drives the transistor T11 with the voltage amplitude of 5V which ishigher than 3V of the driving pulses V1 and V2; prevents the voltagefrom falling in the transistor T11; and enables the bootstrap capacitorC1 to charge up to 3V of the source voltage VDD.

In FIG. 3 at the time T0, when the start pulse VST rises to 5V, thebootstrap capacitor charging transistor T11 of the first stage turns on;and the bootstrap capacitor C1 is charged toward the source voltage VDD.Here, even if the bootstrap capacitor charging transistor T11 is anenhancement type NMOS, without the influence of the threshold voltageVt1 of the transistor T11, the voltage VN11 of the node N11 where thegate of the output transistor T12 is connected is charged up to 3V ofthe source voltage VDD; and the output transistor T12 turns on.

At the time T1, when the driving pulse V1 of 3V is inputted into thedrain of the output transistor T12, the voltage HB1 is applied to thegate (the node N11) of the output transistor T12, said voltage HB1 beingthe combination of the driving pulse V1 of 3V and the potentialdifference between the both ends of the bootstrap capacitor C1 (3V-Vt1);and the pulse of the amplitude H1 is outputted from the node N12.

At the same time, the voltage HB1 of the node N11 is applied to the gateof the bootstrap capacitor charging transistor T21 of the second stage;the transistor T21 turns on; and the bootstrap capacitor C2 is chargedto the source voltage VDD without falling for the threshold voltage ofthe transistor T21. When the charging voltage of the bootstrap capacitorC2 (the node N21) exceeds the threshold voltage of the output transistorT22, the output transistor T22 of the second stage turns on.

Simultaneously, the voltage of the node N21 is applied to the gate ofthe bootstrap capacitor charging transistor T31 of the third stage.Thus, the transistor T31 turns on, and the bootstrap capacitor C3 ischarged to the voltage (3V-Vt3) lowered for the threshold voltage Vt3 ofthe transistor T31. In this state, in the case the driving pulse V1 is3V which is a logical “High” level, when the driving pulse V1 isoutputted to the output node N12 of the first stage, the pulse of theamplitude less than the driving pulse of V1 is also outputted to theoutput node N32 of the third stage. To solve this problem, the plusterminal of the bootstrap capacitor C3 is set close to the earthvoltage; and in order for the output transistor T32 of the third stageto turn off, the error operation preventative transistor T35 isconnected between the plus terminal of the bootstrap capacitor C3 andthe earth voltage. In other words, the drain of the error operationpreventative transistor T35 is connected to the plus terminal of thebootstrap capacitor C3; the source of T35 is connected to the earthvoltage; and the gate is connected to the output node N12 of the firststage. Also, when the driving pulse V1 is appearing in the output nodeN12 of the first stage, the error operation preventative transistor T35is turned on; the potential of the node N31 is set close to the earthvoltage; thereby the driving pulse V1 is prevented from appearing in theoutput node N32 of the third stage.

In the same manner, the plus terminal of the bootstrap capacitor C4 isconnected to the drain of the error operation preventative transistorT45; the earth voltage is connected to the source of the T45; the gateof T45 is connected to the output node N22 of the two stages forward;thus, the error operation is prevented through all the stages.

However, in the processes of a low-voltage driving and a fast operation,it is necessary to set the threshold voltage low for the outputtransistor such as the output transistor T32. In the error operationpreventative method wherein only the plus terminal of the bootstrapcapacitor C3 is set close to the earth voltage, the output transistorsuch as the output transistor T32 turns on; and the voltage with theamplitude lower than V1 and V2 of the driving pulse is outputted to thenode N32 and all the nodes of the backward stages corresponding to thenode N32. Therefore, the pulse output occurs in other places than thedesignated places for the pulse output, and the signal transmissioncircuit does not operate normally. For example, at the time T1, theerror operation preventative transistor T35 has “ON” electricalresistance; the potential of the node N31 does not completely become 0;thus the output transistor T32 turns on.

In the future processes of the low-voltage driving and the fastoperation of the circuit, this error operation will appear prominently.

SUMMARY OF THE INVENTION

An object of the present invention, in view of the above problem, is toprovide a signal transmission circuit which is capable of a stableoperation even in the case where (a) a circuit is connected with asource power of low voltage and (b) a circuit is operated by fastdriving.

In order to achieve such object as described above, the signaltransmission circuit according to the present invention comprises pluralstages of circuit in each of which a pulse voltage according to adriving pulse is sequentially outputted, the circuit of each stageincluding: an output transistor which outputs the pulse voltage to asource, according to the driving pulse; a bootstrap capacitor connectedbetween a gate of the output transistor and the source; a first chargingtransistor whose drain is connected to a power source or an earth lineand whose source is connected to the gate of the output transistor inorder to charge the bootstrap capacitor, wherein in the case where afirst discharging transistor is in the first stage, a start pulse isprovided to the gate of the first discharging transistor, and in thecase where a first discharging transistor is in the second stage orbackward, the gate of the first discharging transistor is connected tothe gate of the output transistor; a first discharging transistor whosedrain is connected to one end of the bootstrap capacitor; a seconddischarging transistor whose drain is connected to the other end of thebootstrap capacitor; and an output transistor control circuit whichprevents the pulse voltage from outputting from the output transistor ofeach circuit of the other stages, in the case the pulse voltage isoutputted from the source of the output transistor.

It is desirable that the output transistor control circuit is a logicalcircuit which (i) turns on the first and second discharging transistors,according to the driving pulse for each circuit of the other stages, and(ii) turns off the first and second discharging transistors, accordingto the gate signal of the charging transistor.

The first and second discharging transistors are turned on, according toa driving pulse for each circuit of the other stages. Therefore, in thecase where a pulse voltage is not outputted from each circuit of thecorresponding stage, it is possible to certainly earth the source of theoutput transistor. On the other hand, in the case where a pulse voltageis outputted from each circuit of the corresponding stage, the first andsecond discharging transistors are turned off. Thus, a pulse voltage canbe outputted from the source of the output transistor.

Also, the gate of the first discharging transistor is further connectedto the source of the output transistor of the next stage; the gate ofthe second discharging transistor is connected to the source of theoutput transistor of the next stage; the output transistor controlcircuit has: a first error operation preventative transistor whose drainis connected to the gate of the output transistor, and whose gate isconnected to the source of the output transistor of the two stagesforward, and a second error operation preventative transistor whosedrain is connected to the source of the output transistor, and whosegate is connected to the source of the output transistor of two stagesforward.

According to such structure as described above, even in the case where apulse voltage is outputted to the source of the output transistor of thethird stage and backward by error operation, the output pulse of the twostages forward is applied to the gate of the second error operationpreventative transistor. Thus, the second error operation preventativetransistor is on. Therefore, it is possible to earth the potential ofthe output pulse of the third stage and backward; thereby it is possibleto prevent the pulse voltage from being caused by error operation of thesource of the output transistor of the third stage and backward.

It is desirable that the circuit of each stage includes a third erroroperation preventative transistor whose drain is connected to the sourceof the output transistor, and whose gate is connected to the source ofthe output transistor of the two stages backward.

According to such structure as described above, even in the case where apulse voltage is outputted to the source of the output transistor of thecircuit of the two stages forward by error operation, a pulse voltage ofthe output pulse is applied to the gate of the third error operationpreventative transistor of the two stages forward. Thus, the third erroroperation preventative transistor is on. Therefore, it is possible toearth the pulse voltage of two stages forward.

Moreover, as for the first discharging transistor, the pulse voltage isapplied to the gate, said pulse voltage being provided from the sourceof the output transistor of the next stage; as for the seconddischarging transistor, the pulse voltage is applied to the gate, saidpulse voltage being provided from the source of the output transistor ofthe next stage; and the output transistor control circuit is a logicalcircuit which (i) outputs the voltage signal of “High” level in the casethe source voltage of the output transistor is “High” level, and (ii)outputs the voltage signal of “Low” level, according to the gate voltageof the output transistor, in the case the source voltage of the outputtransistor is “Low” level.

Because the logical circuit is formed as described above, only in thecircuit of the stage where the original pulse output is caused, thepulse is outputted to the OUT terminal as usual; and in the circuit ofthe other stages, even if the pulse output is caused by error operation,the pulse is stopped by the switch circuit before being outputted to theOUT terminal. Thus, from the viewpoint of the OUT terminal of the signaltransmission circuit, the pulse is normally scanned, and the surroundingcircuit does not receive any bad influence. In other words, it ispossible to provide a signal transmission circuit which can normallyoutput a pulse to the external OUT terminal even if an error operationoccurs inside the signal transmission circuit.

According to the present invention, a pulse voltage is outputted only inthe circuit of the desirable stage, and it is not outputted in thecircuit of the other stages. Therefore, it is possible to stably drivethe signal transmission circuit even in the low-source voltage circuitand fast driving. It is expected to show beneficial effects, inparticular, if applied to an MOS solid image sensor and an LCDapparatus. Consequently, the present invention is considered extremelyprofitable.

FURTHER INFORMATION ABOUT TECHNICAL BACKGROUND TO THIS APPLICATION

The disclosure of Japanese Patent Applications No. 2003-307744 filed onAug. 29, 2003, No. 2003-307745 filed on Aug. 29, 2003 and No.2003-307746 filed on Aug. 29, 2003, each including specification,drawings and claims are incorporated herein by reference in itsentirety.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, advantages and features of the invention willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings that illustrate a specificembodiment of the invention. In the Drawings:

FIG. 1 is a circuit diagram of the conventional signal transmissioncircuit;

FIG. 2 is a circuit diagram of the conventional error operationpreventative signal transmission circuit;

FIG. 3 is an operational time chart of the conventional error operationpreventative signal transmission circuit;

FIG. 4 is a circuit diagram of the error operation preventative signaltransmission circuit according to the first embodiment of the presentinvention;

FIG. 5 is an operational time chart according to the first embodiment ofthe present invention;

FIG. 6 is a circuit diagram of the error operation preventative signaltransmission circuit according to the second embodiment of the presentinvention;

FIG. 7 is a circuit diagram of the error operation preventative signaltransmission circuit according to the third embodiment of the presentinvention;

FIG. 8 is a circuit diagram of the error operation preventative signaltransmission circuit according to the fourth embodiment of the presentinvention;

FIG. 9 is a circuit diagram of the error operation preventative signaltransmission circuit according to the fifth embodiment of the presentinvention;

FIG. 10 is an operational time chart according to the fifth embodimentof the present invention;

FIG. 11 is a circuit diagram of the error operation preventative signaltransmission circuit according to the sixth embodiment of the presentinvention;

FIG. 12 is a circuit diagram of the error operation preventative signaltransmission circuit according to the seventh embodiment of the presentinvention;

FIG. 13 is an operational time chart according to the seventh embodimentof the present invention;

FIG. 14 is a circuit diagram of the error operation preventative signaltransmission circuit according to the eighth embodiment of the presentinvention;

FIG. 15 is a circuit diagram of the error operation preventative signaltransmission circuit according to the other embodiments of the presentinvention; and

FIG. 16 is a block diagram of the solid image sensor comprising theerror operation preventative signal transmission circuit according tothe embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

(First Embodiment)

FIG. 4 is a schematic diagram of the signal transmission circuitaccording to the first embodiment of the present invention.

The signal transmission circuit according to the first embodimentcomprises plural stages of circuit in which each pulse voltage followingthe driving pulse is sequentially outputted from the circuit of eachstage. Here, five stages of circuit are shown. The signal transmissioncircuit according to the present embodiment is different from theconventional signal transmission circuit as shown in FIG. 1 in that eachstage includes a logical circuit. Also, the gates of the firstdischarging transistor and the second discharging transistor areconnected to the logical circuit.

The logical circuit of the “2N−1”th (N is a natural number) stages (i)turn on the first discharging transistor T13 (T33, T53) and the seconddischarging transistor T14 (T34, T54), according to the driving pulse V2for the circuit of the “2N”th stages (N is a natural number), and (ii)turn off the first discharging transistor T13 (T33, T53) and the seconddischarging transistor T14 (T34, T54), according to the gate signal ofthe bootstrap capacitor charging transistor T11 (T31, T51).

The logical circuit of the “2N”th stages (i) turn on the firstdischarging transistor T23 (T43) and the second discharging transistorT24 (T44), according to the driving pulse V1 for the circuit of the“2N−1”th stages and (ii) turn off the first discharging transistor T23(T43) and the second discharging transistor T24 (T44), according to thegate signal of the bootstrap capacitor charging transistor T21 (T41).

According to this structure, only in the circuit of the stages whereinthe proper pulse output occurs, the pulse is outputted to the OUTterminal as usual; and in the circuit of the other stages, the pulseoutput due to error operation does not occur.

Further operations will be explained, referring to FIG. 5. FIG. 5 is anoperational time chart showing the pulse voltage of each unit in thesignal transmission circuit according to the first embodiment of thepresent invention. This circuit is a 3V type circuit, wherein thevoltage amplitude of the driving pulses V1 and V2 and the source voltageVDD are 3V. However, the voltage amplitude of the start pulse VST is 5V.Here, the reason why only the voltage amplitude of the start pulse VSTis 5V is because only in the bootstrap capacitor charging transistor T11of the first stage where the start pulse VST is inputted, the highvoltage from the previous stage cannot be provided. Therefore, only thestart pulse VST drives the transistor T11 with the voltage amplitude of5V which is higher than 3V of the driving pulses V1 and V2; prevents thevoltage from falling in the transistor T11; and enables the bootstrapcapacitor C1 to charge up to 3V of the source voltage VDD.

In FIG. 5 at the time T1, when the start pulse VST rises to 5V, thebootstrap capacitor charging transistor T11 of the first stage turns on;and the bootstrap capacitor C1 is charged toward the source voltage VDD.Here, even if the bootstrap capacitor charging transistor T11 is anenhancement type NMOS, without the influence of the threshold voltageVt1 of the transistor T11, the voltage VN11 of the node N11 where thegate of the output transistor T12 is connected is charged up to 3V ofthe source voltage VDD; and the output transistor T12 turns on.

At the time T2, when the driving pulse V1 of 3V is inputted into thedrain of the output transistor T12, the high voltage HB1 is applied tothe gate (the node N11) of the output transistor T12, said high voltageHB1 being the addition of the driving pulse V1 of 3V and the potentialdifference of 3V between the both ends of the bootstrap capacitor C1;and the driving pulse V1 of the amplitude 3V is certainly outputted asthe output pulse OUT1 from the node N12. At the same time, the voltageHB1 of the node N11 is applied to the gate of the bootstrap capacitorcharging transistor T21 of the second stage; the transistor T21 turnson; and the bootstrap capacitor C2 is charged to the source voltage VDDwithout falling for the threshold voltage of the transistor T21. Whenthe charging voltage of the bootstrap capacitor C2 (the node N21)exceeds the threshold voltage of the output transistor T22, the outputtransistor T22 of the second stage turns on. Simultaneously, the voltageof the node N21 is applied to the gate of the bootstrap capacitorcharging transistor T31 of the third stage. Thus, the transistor T31turns on, and the bootstrap capacitor C3 is charged to the voltage(3V-Vt3) lowered for the threshold voltage Vt3 of the transistor T31. Inthis state, in the case the driving pulse V1 is 3V which is a logical“High” level, when the driving pulse V1 is outputted to the output nodeN12 of the first stage, the pulse of the amplitude less than the drivingpulse of V1 is also outputted to the output node N32 of the third stage.Even in such case as described above, in the present embodiment, onlythe driving pulse V1 of the output node N12 of the first stage isoutputted to the OUT1 terminal; thereby the pulse of the amplitude lowerthan the driving pulse V1 which occurred in the output node N32 of thethird stage does not occur to the OUT3 terminal.

In other words, at the time T0, in the driving pulse V2, the potentialof the logical circuit internal node N13, the node N33 and the node N53is charged to “High”. Then, the first discharging transistor and thesecond discharging transistor turn on. After that, every time thedriving pulse V2 becomes “High”, the charging is repeated; the outputnode N12, the node N32, and the node N53 are earthed; thus the pulseoutput does not appear in the OUT terminal. However, at the time T1,when the start pulse VST becomes “High”, the potential of the logicalcircuit internal node N13 of the first stage is discharged to “Low”;thereby the first discharging transistor and the second dischargingtransistor turn off. At the time T2, when the driving pulse V1 becomes“High”, the output node N12 is not earthed; thereby the pulse outputappears in the OUT terminal. At the time T3, again, in the driving pulseV2, the potential of the logical circuit internal node N13 is charged to“High”. After that, every time the driving pulse V2 becomes “High”, thecharging is repeated; thereby the output node N12 remains earthed.Simultaneously, in the logical circuit internal node N33 and the nodeN53, every time the driving pulse V2 becomes “High”, the charging isrepeated; thus the output nodes N32 and N52 remain earthed. At the timeT4, when the driving pulse V1 becomes “High”, the potential of thelogical circuit internal node N33 of the third stage is discharged to“Low”; the first discharging transistor and the second dischargingtransistor turn off; the output node N32 is not earthed; and the pulseoutput appears in the OUT terminal.

At the time T5, again, in the driving pulse V2, the potential of thelogical circuit internal node N33 is charged to “High”. After that,every time the driving pulse V2 becomes “High”, the charging isrepeated; thereby the output node N32 remains earthed. The output nodeN53 and the like repeat the same operations as described above. As forthe circuit of the “2N”th stages such as the output node N22 and thenode N42, every time the driving pulse V1 becomes “High”, the logicalcircuit internal node N23 and N43 are charged; thereby the output nodesremain earthed. However, only at the times when the first chargingtransistor of the circuit of each stage turns on, the logical circuitinternal nodes N23, N43 and the like are discharged; and the pulseoutput appears in each OUT terminal. As described above, only when thefirst charging transistor of the circuit of each stage is on, the pulseis outputted from the output node of the circuit of each stage; at othertimes, the pulse output does not appear.

Consequently, it is possible to provide a signal transmission circuitcapable of a stable operation even with a circuit source power of lowvoltage and a fast driving.

(Second Embodiment)

FIG. 6 is a structure example of the signal transmission circuitaccording to the second embodiment of the present invention. The signaltransmission circuit according to the second embodiment shows thelogical circuit units of the first embodiment in further detail.

The logical circuit of the “2N−1”th stages include the voltage holdingcapacitor C100 (C300, C500), the second charging transistor T101 (T301,T501) and the third discharging transistor T102 (T302, T502). The secondcharging transistor T101 (T301, T501) connects: each drain and eachsource: each gate and the driving pulse V2 for each circuit of “2N”thstages: and each source and the voltage holding capacitor C100 (C300,C500). The third discharging transistor connects: each drain and eachsource of the second charging transistor T101 (T301, T501): each gateand each gate of the bootstrap capacitor charging transistor T11 (T31,T51): and each source and the earth line.

The logical circuit of the “2N”th stages include the voltage holdingcapacitor C200 (C400), the second charging transistor T201 (T401) andthe third discharging transistor T202 (T402). The second chargingtransistor T201 (T401) connects: each drain and each source: each gateand the driving pulse V1 for each circuit of “2N−1”th stages: and eachsource and the voltage holding capacitor C200 (C400). The thirddischarging transistor connects: each drain and each source of thesecond charging transistor T201 (T401): each gate and each gate of thebootstrap capacitor charging transistor T21 (T41): and each source andthe earth line.

In both the circuit of the “2N”th stages and the circuit of the “2N−1”thstages, in the voltage holding capacitor C100-C500 included in Thelogical circuit, one end of each electrodes is connected to each sourceof the second charging transistor T101-T501 and each drain of the thirddischarging transistor T102-T502; the other end of each electrode isconnected to the earth line; and the sources of the second chargingtransistor T101-T501 and the drains of the third discharging transistorT102-T502 are connected to the gates of the first discharging transistorT13-T53 and the second discharging transistor T101-T501.

The operations of such signal transmission circuit as described abovewill be explained as following.

In the first stage, in the second charging transistor T101, when thedriving pulse V2 becomes “High”, the voltage holding capacitor C100starts charging; the first discharging transistor T13 and the seconddischarging transistor T14 turn on; and the output node N12 is earthed.When the start pulse VST becomes “High”, the voltage holding capacitorC100 starts discharging; the first discharging transistor T13 and thesecond discharging transistor T14 turn off; and the potential of theoutput node N12 is outputted to the OUT terminal. As for the circuit ofthe “2N−1”th stages, when the driving pulse V2 becomes “High”, thevoltage holding capacitor starts charging; the first dischargingtransistor and the second discharging transistor turn on; and the outputnode is earthed. When the gate of the first charging transistor becomes“High”, the voltage holding capacitor starts discharging; the firstdischarging transistor and the second discharging transistor turn off;and the potential of the output node is outputted to the OUT terminal.

As for the circuit of the “2N”th stages, when the driving pulse V1becomes “High”, the voltage holding capacitor starts charging; the firstdischarging transistor and the second discharging transistor turn on;and the output node is earthed. When the gate of the first chargingtransistor becomes “High”, the voltage holding capacitor startsdischarging; the first discharging transistor and the second dischargingtransistor turn off; and the potential of the output node is outputtedto the OUT terminal

As described above, according to the present embodiment, only when thefirst charging transistor of the circuit of each stage is on, the pulseis outputted from the output node of the circuit of each stage; at othertimes, the pulse output does not appear.

Consequently, it is possible to provide the signal transmission circuitcapable of the stable operation in the state of the low voltage of thecircuit source and the fast driving.

(Third Embodiment)

FIG. 7 is a structure example of the signal transmission circuitaccording to the third embodiment of the present invention.

The signal transmission circuit comprises plural stages of circuit,wherein each pulse voltage according to the driving pulse issequentially outputted. Here, the circuit structure of the five stagesis shown.

The error operation preventative signal transmission circuit isdifferent from the conventional error operation preventative signaltransmission circuit as shown in FIG. 1 in that in the third andbackward stages the second error operation preventative transistor T36(T46, T56) are set. For example, the drain of the second error operationpreventative transistor T36 is connected to the source of the outputtransistor T32 of the same stage; the gate of the second error operationpreventative transistor T36 is connected to the source of the outputtransistor T12 of the two stages forward; and the source is earthed.

According to this structure, even if the pulse voltage is outputted tothe sources of the output transistor T32 (T42, T52) of the third andbackward stages, due to error operation, the output pulse of the twostages forward is applied to the gate of the second error operationpreventative transistor T36 (T46, T56); thereby the second erroroperation preventative transistor T36 (T46, T56) are on. Consequently,it is possible to make each potential of the output pulse of the thirdand backward stages the earth voltage; thus the pulse voltage isprevented from occurring, due to error operation of the source of theoutput transistor of the third and backward stages.

(Fourth Embodiment)

FIG. 8 is a structure example of the signal transmission circuitaccording to the fourth embodiment of the present invention.

In the present embodiment, in addition to the error operationpreventative measures of the third embodiment, when the output pulse isoutputted from the corresponding output transistor, the output pulse isprevented from outputting from the output transistor of the circuitwhich is more than two stages forward.

Therefore, the signal transmission circuit is equipped with the thirderror operation preventative transistor T17 (T27, T37, T47, T57), inaddition to the signal transmission circuit as shown in FIG. 7.

For example, in the third error operation preventative transistor T17,the drain of T17 is connected to the source of the output transistorT12; the gate is connected to the source of the two-stage forward outputtransistor T32; and the source is earthed.

As the fast operation of the circuit advances, the time for dischargingthe bootstrap capacitor C1-C5 is shortened. However, if sufficientdischarging time is not provided, some electric charge remains withoutdischarging in the bootstrap capacitor C1-C5. Due to this residualelectric charge in the bootstrap capacitor C1-C5, if the voltage higherthan the threshold voltage of the output transistor T12-T52 is appliedto the gate of the output transistor T12-T52, the pulse voltage may beoutputted to the sources of the two-stage forward output transistorT12-T52, due to error operation.

For the fast operation of the circuit, each threshold voltage of theoutput transistor T12-T52 is often set low, and the probability of erroroperation becomes high. As for the operation of the fourth embodiment,the case in which the desired pulse voltage is outputted to the outputpulse OUT 3 will be explained as an example. In this case, even if thepulse voltage is outputted to the source of the two-stage forward outputtransistor T12, due to error operation, the pulse voltage of the outputpulse OUT3 is applied to the gate of the two-stage forward third erroroperation preventative transistor T17; thus the third error operationpreventative transistor T17 is on. Therefore, it is possible to make thetwo-stage forward pulse voltage the earth voltage.

Thus, according to the present embodiment, when the desired pulsevoltage is outputted, even if the pulse voltage is outputted to thesource of the two-stage forward output transistor, due to erroroperation, the third error operation preventative transistor is on.Consequently, it is possible to prevent the pulse voltage from occurringto the source of the two-stage forward output transistor, due to erroroperation.

(Fifth Embodiment)

FIG. 9 is a structure example of the signal transmission circuitaccording to the fifth embodiment of the present invention. In additionto the measures of the third and fourth embodiments, the fifthembodiment utilizes measures to prevent the output pulse from outputtingfrom the output transistor placed more than four stages backward fromthe corresponding output transistor before the output pulse is outputtedfrom the corresponding output transistor.

In addition to the signal transmission circuit shown in FIG. 8, thesignal transmission circuit shown in FIG. 9 comprises the voltageholding capacitor C100-C300, the voltage holding capacitor chargingtransistor T100-T300, the third discharging transistor T101-T301 and thefourth error operation preventative transistor T102-T302.

For example, as for the voltage holding capacitor charging transistorT100, the pulse voltage sequentially outputted from the correspondingoutput transistor T12 is applied to the gate; the drain is connected tothe source line; and the source is connected to the plus terminal of thevoltage holding capacitor C100.

Also, as for the third discharging transistor T101, the pulse voltage ofthe two stages backward from the corresponding output transistor T12 isapplied to the gate and the drain is connected to the plus terminal ofthe voltage holding capacitor C100.

Furthermore, as for the fourth error operation preventative transistorT102, the drain is connected to the gate of the output transistor T15which is four stages backward from the corresponding output transistorT12; and the gate is connected to the plus terminal of the voltageholding capacitor C100.

The specific operations will be further explained referring to FIG. 10.FIG. 10 is a time chart showing the pulse voltage of each unit in thesignal transmission circuit according to the fifth embodiment. Thiscircuit is a 3V type circuit, wherein the voltage amplitude of thedriving pulses V1 and V2 and the source voltage VDD are 3V. However, thevoltage amplitude of the start pulse VST is 5V. The reason why only thevoltage amplitude of the start pulse VST is 5V is because only in thebootstrap capacitor charging transistor T1 of the first stage where thestart pulse VST is inputted, the high voltage from the previous stagecannot be provided; thus only the start pulse VST drives the transistorT11 with 5V higher than 3V, the voltage amplitude of the driving pulsesV1 and V2; thereby the voltage is prevented from falling in thetransistor T11; and the bootstrap capacitor C1 is enabled to be chargedto 3V of the source voltage VDD.

In FIG. 10 at the time T0, when the start pulse VST rises to 5V, thebootstrap capacitor charging transistor T11 of the first stage turns on;thus the bootstrap capacitor C1 starts to get charged toward the sourcevoltage VDD. Here, in the case the bootstrap capacitor chargingtransistor T11 is an enhancement type, NMOS, because of the influence ofthe threshold voltage Vt1 of the transistor T11, the voltage VN11 of thenode N11 where the gate of the output transistor T12 is connectedbecomes the voltage (3V-Vt1) which is lower than 3V of the sourcevoltage VDD by the threshold voltage Vt1; and in this state the outputtransistor T12 turns on.

At the time T1, when the driving pulse V1 of 3V is inputted into thedrain of the output transistor T12, the voltage HB1 which is thecombination of the voltage 3V of the driving pulse V1 and the potentialdifference of the both ends of the bootstrap capacitor C1 (3V-Vt) isapplied to the gate (the node N11) of the output transistor T12; and thepulse with the amplitude of H1 is outputted from the node N12.

At the same time, the voltage HB1 of the node N11 is applied to the gateof the bootstrap capacitor charging transistor T21 of the second stage;thereby the transistor T21 turns on. Then, the bootstrap capacitor C2 ischarged to the source voltage VDD which does not fall for the thresholdvoltage of the transistor T21. When the charging voltage (the node N21)of the bootstrap capacitor C2 exceeds the threshold voltage of theoutput transistor T22, the output transistor T22 of the second stageturns on. Simultaneously, the voltage of the node N21 is applied to thegate of the bootstrap capacitor charging transistor T31 of the thirdstage. Therefore, the transistor T31 turns on; and the bootstrapcapacitor C3 is charged up to the voltage (3V-Vt3) which is lower than3V of the source voltage VDD by the threshold voltage Vt3.

In this state, in the case the driving pulse V1 is 3V of the logical“High” level, when the driving pulse V1 is outputted to the output nodeN12 of the first stage, at the same time, the pulse with the amplitudeless than the driving pulse V1 is outputted to the output node N32 ofthe third stage. To solve this problem, the electric potential of theplus terminal of the bootstrap capacitor C3 is set close to the earthvoltage; and in order for the output transistor T32 of the third stageto turn off, the error operation preventative transistor T35 isconnected between the plus terminal of the bootstrap capacitor C3 andthe earth voltage. In other words, the drain of the error operationpreventative transistor T35 is connected to the plus terminal of thebootstrap capacitor C3; the source is connected to the earth voltage;and the gate is connected to the output node N12 of the first stage. Inthis manner, when the driving pulse V1 appears in the output node N12 ofthe first stage, the error operation preventative transistor T35 turnson; the node N31 is set close to the earth voltage; and the drivingpulse V1 is prevented from appearing in the output node N32 of the thirdstage.

Also, the drain of the error operation preventative transistor T45 isconnected to the plus terminal of the bootstrap capacitor C4 of thebackward stage; the source of the error operation preventativetransistor T45 is connected to the earth voltage; the gate of the erroroperation preventative transistor T45 is connected to the output nodeN22 of the two stages forward; thereby the error operation is preventedthrough all the stages. However, in the processes of the low-voltagedriving and the fast operations of the circuit, it is necessary to setthe threshold voltage of the output transistor such as the outputtransistor T32; and the voltage applied to the gate of the outputtransistor T52 must be set as close the amount as the earth voltage.

In other words, at the time T1, when the driving pulse V1 of 3V isinputted into the drain of the output transistor T12, the voltage HB1 isapplied to the gate (the node N11) of the output transistor T12, saidvoltage HB1 being the combination of 3V of the voltage of the drivingpulse V1 and the potential difference (3V-Vt) of the both ends of thebootstrap capacitor C1. At the same time, the voltage HB1 of the nodeN11 is applied to the gate of the bootstrap capacitor chargingtransistor T21 of the second stage; and the transistor T21 turns on.Then, the bootstrap capacitor C2 (the node N21) is charged to the sourcevoltage VDD which does not fall for the threshold voltage of thetransistor T21. Here, at the same time, the voltage of the node N21 isapplied to the gate of the bootstrap capacitor charging transistor T31of the third stage; and the transistor T31 turns on. Then, the bootstrapcapacitor C3 (the node N31) is charged to the voltage (3V-Vt3) which islower than 3V of the source voltage VDD by Vt3 of the threshold voltageof the transistor T31. At the same time, the voltage of the node N31 isapplied to the gate of the bootstrap capacitor charging transistor T41of the fourth stage; and the transistor T41 turns on. Then, thebootstrap capacitor C4 (the node N41) is charged to the voltage(3V-Vt3-Vt4) which is lower than 3V of the source voltage VDD by Vt3 andVt4 of the threshold voltage of the transistor T31 and T41. At the sametime, the voltage of the node N41 is applied to the gate of thebootstrap capacitor charging transistor T51 of the fifth stage; and thetransistor T51 turns on. Then, the bootstrap capacitor C5 (the node N51)is charged to the voltage (3V-Vt3-Vt4-Vt5) which is lower than 3V of thesource voltage VDD by Vt3, Vt4 and Vt5 of the threshold voltage of thetransistor T31, T41 and T51.

In this state, in the case the driving pulse V1 is 3V of the logical“High” level, when the driving pulse V1 is outputted to the output nodeN12 of the first stage, at the same time, the pulse with the amplitudeless than the driving pulse V1 might be outputted to the output node N52of the fifth stage. To solve this problem, the plus terminal of thebootstrap capacitor C5 is set close to the earth voltage; and in orderfor the output transistor T52 of the fifth stage to turn off, the fourtherror operation preventative transistor T102 is connected between theplus terminal of the bootstrap capacitor C5 and the earth voltage. Asfor the fourth error operation preventative transistor T102, when thedesired pulse voltage is outputted, the charging transistor T100 turnson; the capacitor C100 is charged with the voltage around the VDDvoltage; the fourth error operation preventative transistor T102 turnson; and the output transistor of the fifth stage is controlled in orderfor the source of the T52 to discharge. The pulse voltage of the thirdstage is outputted; the discharging transistor T101 turns on; thecapacitor C100 is discharged; and the fourth error operationpreventative transistor T102 is controlled to be off.

According to the fifth embodiment, even in the case the thresholdvoltage of the output transistor is low; the error operation can beprevented; thus the range of the threshold voltage can be large.

(Sixth Embodiment)

FIG. 11 is a schematic diagram of the signal transmission circuitaccording to the sixth embodiment of the present invention. The signaltransmission circuit comprises plural stages of circuit; and the pulsevoltage according to the driving pulse is sequentially outputted fromthe circuit of each stage. FIG. 11 shows only five stages.

The signal transmission circuit in FIG. 11 is different from theconventional signal transmission circuit in FIG. 1 in that each circuitincludes a logical circuit. In the case the source voltage of the outputtransistor T12 (T22-T52) is at “High” level the logical circuit outputsthe voltage signal of “High” level; and in the case the source voltageof the output transistor T12 (T22-T52) is at “Low” level, the logicalcircuit outputs the voltage signal of “Low” level, according to the gatevoltage of the output transistor T12 (T22-T52).

According to this structure, only in the circuit of the stages where theoriginal pulses are caused, the pulses are outputted to the OUT terminalas usual; in the circuit of the other stages, even if the pulses areoutputted by error operation, the output pulses are blocked by theswitching circuit. Thus, from the viewpoint of the OUT terminals of thesignal transmission circuit, the pulses are scanned normally; and thesurrounding circuit is free from any bad influence. In other words, itis possible to provide the signal transmission circuit which can outputthe pulses to the external OUT terminals as usual, even if erroroperation occurs inside the signal transmission circuit.

(Seventh Embodiment)

FIG. 12 is a structure example of the signal transmission circuitaccording to the seventh embodiment of the present invention. In thissignal transmission circuit, The logical circuit of the signaltransmission circuit according to the sixth embodiment are embodied. InFIG. 12 The logical circuit includes the first transistor T101(T201-T501), the inverter circuit, the second transistor T102(T202-T502), the third transistor T103 (T203-T503), and the fourthtransistor T104 (T204-T504).

In the first transistor T101 (T201-T501), each drain is connected to thepower source; and each gate is connected to each source of the outputtransistor T12 (T22-T52). The inverter circuit receive each gate of theoutput transistor T12 (T22-T52) as the input. In the second transistorT102 (T202-T502), each gate is connected to the output of the invertercircuit. In the third transistor T103 (T203-T503), each drain isconnected to the source of the output transistor of the circuit of eachstage; each gate is connected to the source of the transistor T102(T202-T502); and each source is connected to the earth line. In thefourth transistor T104 (T204-T504), each gate is connected to each gateof the output transistor T12 (T22-T52); each drain is connected to eachgate of the transistor T103 (T203-T503). Also, each source of the firsttransistor T101 (T201-T501) is connected to each drain of the secondtransistor T102 (T202-T502).

The specific operations of the signal transmission circuit as shown inFIG. 12 will be explained, referring to FIG. 13. FIG. 13 is a time chartshowing the pulse voltage of each unit in the signal transmissioncircuit according to the seventh embodiment. This circuit is a 3V typecircuit, wherein the voltage amplitude of the driving pulses V1 and V2and the source voltage VDD are 3V. However, the voltage amplitude of thestart pulse VST is 5V. Here, the reason why only the voltage amplitudeof the start pulse VST is 5V is because only in the bootstrap capacitorcharging transistor T11 of the first stage where the start pulse VST isinputted, the high voltage of the previous stage cannot be provided.Thus, only the start pulse VST drives the transistor T11 with thevoltage amplitude 5V which is higher than 3V of the driving pulses V1and V2; the voltage is prevented from falling in the transistor T11; andit is possible to charge the bootstrap capacitor C1 to 3V of the sourcevoltage VDD.

In FIG. 13 at the time T0, when the start pulse VST rises to 5V, thebootstrap capacitor charging transistor T11 of the first stage turns on;and the bootstrap capacitor C1 starts to get charged toward the sourcevoltage VDD. Here, even if the bootstrap capacitor charging transistorT11 is an enhancement type, NMOS, without the influence of the thresholdvoltage Vt1 of the transistor T11, the voltage VN11 of the node N11 ischarged to 3V of the source voltage VDD, said node N11 being connectedto the gate of the output transistor T12; and the output transistor T12turns on.

Next, at the time T1, when the driving pulse V1 of 3V is inputted intothe drain of the output transistor T12, the high voltage HB1 is appliedto the gate (the node N11) of the output transistor T12, said voltageHB1 being the combination of 3V of the driving pulse V1 and 3V of thepotential difference of the both ends of the bootstrap capacitor C1; andthe driving pulse V1 of the amplitude 3V is certainly outputted as theoutput pulse OUT1 from the node N12. At the same time, the voltage HB1of the node N11 is applied to the gate of the bootstrap capacitorcharging transistor T2 of the second stage; and the transistor T21 turnson. Then, the bootstrap capacitor C2 is charged to the source voltageVDD which does not fall for the threshold voltage of the transistor T21.When the charging voltage (the node N21) of the bootstrap capacitor C2exceeds the threshold voltage of the output transistor T22, the outputtransistor T22 of the second stage turns on. At the same time, thevoltage of the node N21 is applied to the gate of the bootstrapcapacitor charging transistor T31 of the third stage. Thus, thetransistor T31 turns on; and the bootstrap capacitor C3 is charged tothe voltage (3V-Vt3) which is lower than 3V of the source voltage VDD bythe threshold voltage Vt3. In this state, in the case the driving pulseV1 is 3V of the logical “High” level, when the driving pulse V1 isoutputted to the output node N12 of the first stage, at the same time,the pulse with the amplitude lower than the driving pulse V1 isoutputted to the output node N32 of the third stage. In such case asdescribed above, according to the seventh embodiment, only the drivingpulse V1 of the output node N12 of the first stage is outputted to theOUT terminal; and the pulse with the amplitude lower than the drivingpulse V1 cannot be caused to the OUT3 terminal, said driving pulse V1being caused in the output node N32 of the third stage.

In other words, in order to output the potential of the node N12 of thefirst stage to the OUT1 terminal, at the time T1, the third transistorT103 of the first stage is turned off; and the third transistor T303,T403 and the like of the third stage and the stages backward of thethird stage.

In other words, the operations of each node of the circuit of each stageare as following: (i) the gate voltage (the node N11) of the outputtransistor T11 is at “High” level, (ii) the voltage is applied to thegate of the fourth transistor T104, and (iii) the turnover voltage of“Low” level is applied to the gate of the second transistor T102. Thus,the gate of the third transistor T103 becomes “Low” level; and it ispossible to output the driving pulse V1 to the OUT1 terminal by thesource voltage (the node N12) of the output transistor T11.

On the other hand, the operations of each node of the circuit of thethird stage are as following: (i) the gate voltage (the node N31) of theoutput transistor T31 is at “Low” level, (ii) the voltage is applied tothe gate of the fourth transistor T304, and (iii) the turnover voltageof “High” level is applied to the gate of the second transistor T302.Thus, the gate of the third transistor T303 becomes “High” level in thecase the pulse with the amplitude less than the driving pulse V1 isoutputted to the source voltage (the node N32) of the output transistor;and the first transistor T301 turns on. Even if the pulse with theamplitude less than the driving pulse V1 is outputted to the sourcevoltage (the node N32) of the output transistor, the gate of the thirdtransistor T303 can make the OUT3 terminal the ground level. Thus, onlythe pulse output is outputted to the OUT terminal. As for the inputlogical level of the inverter circuit which generates the gate turnovervoltage of the output transistor of the circuit of each stage, settingthe input “High” level a high voltage can contribute to the operationalstability. Also, as for the threshold voltage of the first transistor ofthe circuit of each stage, setting the input “High” level a low voltagecan contribute to the operational stability.

(Eighth Embodiment)

FIG. 14 is a structure example of the signal transmission circuitaccording to the eighth embodiment of the present invention. The signaltransmission circuit in FIG. 14 comprises the embodied inverter circuitof the signal transmission circuit in FIG. 12.

The inverter circuit includes the fifth transistor T105 (T205-T505), thesixth transistor T106 (T206-T506), the second bootstrap capacitor C100(C200-C500), and the seventh transistor T107 (T207-T507).

As for the fifth transistor T105 (T205-T505), each gate and each drainare connected to the power source. As for the sixth transistor T106(T206-T506), each drain is connected to the power source, and each gateis connected to each source of the fifth transistor T105 (T205-T505).The both ends of the second bootstrap capacitor C100 (C200-C500) arerespectively connected to the gate and the source of the sixthtransistor T106 (T206-T506). As for the seventh transistor T107(T207-T507), each drain is connected to the source of the fifthtransistor T105 (T205-T505), and each gate is connected to each gate ofthe output transistor T12 (T22-T52) of the circuit of each stage. Thenode is connected to each gate of the second transistor T102(T202-T502), said node being each source of the sixth transistor T106(T206-T506) and each drain of the seventh transistor T107 (T207-T507).

In other words, the inverter circuit which forms the gate turnovervoltage of the output transistor T12 (T22-T52) of the circuit of eachstage only by NMOS are used. In the inverter circuit, setting eachthreshold voltage of the seventh transistor T107 (T207-T507) high cancontribute to the better operational stability. Also, it is desirable toset each threshold voltage of the seventh transistor T107 (T207-T507) ofthe circuit of each stage higher than each threshold voltage of thefirst transistor T101 (T201-T501).

Moreover, it is desirable (i) to set each channel length of the seventhtransistor T107 (T207-T507) shorter than each channel length of thefirst transistor T101 (T201-T501) and (ii) to set the resistance valueof the first transistor T101 (T201-T501) lower than that of the seventhtransistor T107 (T207-T507).

The power source can be commonly connected to all the signaltransmission circuits, said power source being connected to (i) eachdrain of the first transistor T101 (T201-T501) of the circuit of eachstage, (ii) each drain and gate of the fifth transistor T105(T205-T505), and (iii) each drain of the sixth transistor T106(T206-T506).

Also, as FIG. 15 shows, the node can be commonly connected to all thesignal transmission circuits, said node being connected to (i) eachsource of the first transistor T101 (T201-T501) of the circuit of eachstage and (ii) each drain of the second transistor T102 (T202-T502).

According to the sixth, seventh and eighth embodiments, each source ofthe discharging transistor and the error operation preventativetransistor is the earth voltage (0V); however, as for each sourcevoltage, it is possible to acquire the similar effects, even if thevoltage lower than the threshold voltage of the output transistor isprovided to each source of the first error operation preventativetransistor and the first discharging transistor.

It is possible to utilize such signal transmission circuit as describedabove as a shift register for a solid image sensor or liquid crystaldisplay (LCD) apparatus. FIG. 16 shows an example of such solid imagesensor.

The solid image sensor comprises: a lens 102 collecting lights, pixelunits 108 accumulating the collected lights, vertical shift registers106 and 110 for accessing each row of the pixel units 108, a noiseremoval unit 114 for eliminating noise component of the pixel valuedetected from the pixel units 108, a horizontal shift register 116 foraccessing the pixel value for each column and outputting the pixel valuefor each pixel, an amplifier 118 for amplifying the detected pixelvalue, an A/D converter 120 for A/D converting the detected pixel value,and a timing generator 112 for generating the timings for detecting thepixel value from each pixel.

It is possible to accurately detect the pixel value by utilizing thesignal transmission circuit according to an embodiment of the presentinvention for such solid image sensor as described above. Also, it ispossible to apply the signal transmission circuit to the LCD apparatus.

The signal transmission circuit according to the embodiments of thepresent invention has been explained as above; however, the presentinvention is not limited to these embodiments.

For example, in the first and second embodiments, only NMOS can be usedfor the transistor; NMOS capacitor can be used for the capacitor; andall the circuit elements can be formed by NMOS.

Also, in the first and second embodiments, it is desirable to set thethreshold voltage of the output transistor the lowest in the circuit ofeach stage.

In addition, in the first and second embodiments, it is possible toacquire the similar effects even if the potential of the source of thethird discharging transistor is set lower than the threshold voltages ofthe first discharging transistor and the second discharging transistor.

Moreover, in the first and second embodiments, it is possible to acquirethe similar effects even if the voltage lower than the threshold voltageof the output transistor is provided to the source of the firstdischarging transistor.

In the third, fourth and fifth embodiments, each source of thedischarging transistor and error operation preventative transistor isthe earth voltage (0V); however, as for each source voltage, it ispossible to acquire similar effects even if the voltage lower than thethreshold voltage of the fourth error operation preventative transistoris provided to the source of the third discharging transistor in thefifth embodiment.

Also, it is possible to acquire the similar effects even if the voltagelower than the threshold voltage of the output transistor is provided toeach source of the error operation preventative transistor and the firstdischarging transistor in the third, fourth and fifth embodiments.

Although only some exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention.

INDUSTRIAL APPLICABILITY

The signal transmission circuit of the present invention can be utilizedfor the MOS solid image sensor and LCD apparatus which need low powerconsumption and fast operation.

1. A signal transmission circuit comprising plural stages of circuitfrom each of which a pulse voltage according to a driving pulse issequentially outputted, the circuit of each stage including: an outputtransistor which outputs the pulse voltage to a source of the outputtransistor, according to the driving pulse; a bootstrap capacitorconnected between a gate of the output transistor and the source; afirst charging transistor whose drain is connected to a power source oran earth line and whose source is connected to the gate of the outputtransistor in order to charge the bootstrap capacitor, wherein in thecase where a first discharging transistor is in the first stage, a startpulse is provided to the gate of the first discharging transistor, andin the case where the first discharging transistor is in the secondstage or backward, the gate of the first discharging transistor isconnected to the gate of the output transistor of the forward stage; afirst discharging transistor whose drain is connected to one end of thebootstrap capacitor; a second discharging transistor whose drain isconnected to the other end of the bootstrap capacitor; and an outputtransistor control circuit which prevents the pulse voltage from beingoutputted from the output transistor of each circuit of the otherstages, in the case the pulse voltage is outputted from the source ofthe output transistor.
 2. The signal transmission circuit according toclaim 1, wherein the output transistor control circuit is a logicalcircuit which (i) turns on the first and second discharging transistors,according to the driving pulse for each circuit of the other stages, and(ii) turns off the first and second discharging transistors, accordingto the gate signal of the charging transistor.
 3. The signaltransmission circuit according to claim 2, wherein the logical circuithas: a voltage holding capacitor; a second charging transistor whosedrain is connected to a power source, whose gate is provided with adriving pulse of the circuit of each stage, and whose source isconnected to the voltage holding capacitor; a third dischargingtransistor whose drain is connected to the source of the second chargingtransistor, whose gate is connected to the gate of the first chargingtransistor, and whose source is connected to the earth line, wherein asfor the voltage holding capacitor, (i) one of the electrodes isconnected to the source of the second charging transistor and the drainof the third discharging transistor, (ii) the other of the electrodes isconnected to the earth line, (iii) the source of the second chargingtransistor is connected to the gate of the first discharging transistor,and (iv) the drain of the third discharging transistor is connected tothe gate of the second discharging transistor.
 4. The signaltransmission circuit according to claim 3, wherein the electricpotential of the source of the third discharging transistor is set lowerthan the threshold voltages of the first and second dischargingtransistors.
 5. The signal transmission circuit according to claim 2,wherein all transistors and all capacitors are formed by NMOS.
 6. Thesignal transmission circuit according to claim 2, wherein the thresholdvoltage of the output transistor is set the lowest in the circuit ofeach stage.
 7. The signal transmission circuit according to claim 2,wherein all the transistors are NMOS, and each source of the first tothird discharging transistors is connected to the earth voltage.
 8. Thesignal transmission circuit according to claim 2, wherein all thetransistors are NMOS, and the source of the first discharging transistoris provided with the voltage lower than the threshold voltage of theoutput transistor.
 9. The signal transmission circuit according to claim1, wherein the gate of the first discharging transistor is furtherconnected to the source of the output transistor of the next stage; thegate of the second discharging transistor is connected to the source ofthe output transistor of the next stage; the output transistor controlcircuit has: a first error operation preventative transistor whose drainis connected to the gate of the output transistor, and whose gate isconnected to the source of the output transistor of the two stagesforward, and a second error operation preventative transistor whosedrain is connected to the source of the output transistor, and whosegate is connected to the source of the output transistor of two stagesforward.
 10. The signal transmission circuit according to claim 9,wherein the circuit of each stage includes a third error operationpreventative transistor whose drain is connected to the source of theoutput transistor, and whose gate is connected to the source of theoutput transistor of the two stages backward.
 11. The signaltransmission circuit according to claim 9, wherein the circuit of eachstage includes: a charging capacitor; a second charging transistor (i)to whose gate the pulse voltage is applied, said pulse voltage beingsequentially outputted from the corresponding output transistor, (ii)whose drain is connected to the power source line, and (iii) whosesource is connected to the plus terminal of the charging capacitor; athird discharging transistor (i) to whose gate the pulse voltage isapplied, said pulse voltage being of the two stages backward from thecorresponding output transistor, and (ii) whose drain is connected tothe plus terminal of the charging capacitor; and a fourth erroroperation preventative transistor (i) whose drain is connected to thegate of the output transistor which is four stages backward from thecorresponding output transistor, and (ii) whose gate is connected to theplus terminal of the charging capacitor.
 12. The signal transmissioncircuit according to claim 11, wherein all the transistors are NMOS, andthe source of the third discharging transistor is provided with thevoltage lower than the threshold voltage of the fourth error operationpreventative transistor.
 13. The signal transmission circuit accordingto claim 9, wherein said all transistor are NMOS, and each source of thefirst to third discharging transistors is connected to the earthvoltage.
 14. The signal transmission circuit according to claim 9,wherein all the transistors are NMOS, and the source of the first erroroperation preventative transistor is connected to the earth voltage. 15.The signal transmission circuit according to claim 9, wherein said alltransistor are NMOS, and each source of the first error operationpreventative transistor and the first discharging transistor is providedwith the voltage lower than the threshold voltage of the outputtransistor.
 16. The signal transmission circuit according to claim 1,wherein as for the first discharging transistor, the pulse voltage isapplied to the gate, said pulse voltage being provided from the sourceof the output transistor of the next stage; as for the seconddischarging transistor, the pulse voltage is applied to the gate, saidpulse voltage being provided from the source of the output transistor ofthe next stage; and the output transistor control circuit is a logicalcircuit which (i) outputs the voltage signal of “High” level in the casethe source voltage of the output transistor is “High” level, and (ii)outputs the voltage signal of “Low” level, according to the gate voltageof the output transistor, in the case the source voltage of the outputtransistor is “Low” level.
 17. The signal transmission circuit accordingto claim 16, wherein the logical circuit has: a first transistor (i)whose drain is connected to the power source, and (ii) whose gate isconnected to the source of the output transistor; an inverter whichreceives the gate of the output transistor as the input; a secondtransistor whose gate is connected to the output terminal of theinverter; a third transistor (i) whose drain is connected to the sourceof the output transistor of the circuit of each stage, (ii) whose gateis connected to the source of the second transistor, and (iii) whosesource is connected to the earth line; a fourth transistor (i) whosegate is connected to the gate of the output transistor of the circuit ofeach stage, and (ii) whose drain is connected to the gate of the thirdtransistor; and the source of the first transistor is connected to thedrain of the second transistor.
 18. The signal transmission circuitaccording to claim 17, wherein the inverter has: a fifth transistorwhose gate and drain are connected to the power source; a sixthtransistor (i) whose drain is connected to the power source, and (ii)whose gate is connected to the source of the fifth transistor; a secondbootstrap capacitor whose ends are respectively connected to the gateand source of the sixth transistor; a seventh transistor (i) whose drainis connected to the source of the fifth transistor, and (ii) whose gateis connected to the gate of the output transistor of the circuit of eachstage; and the node is connected to the gate of the second transistor,said node being the source of the sixth transistor and the drain of theseventh transistor, and said source and drain being connected to eachother.
 19. The signal transmission circuit according to claim 18,wherein the threshold voltage of the seventh transistor is equal to orhigher than the threshold voltage of the first transistor.
 20. Thesignal transmission circuit according to claim 18, wherein (i) thechannel length of the seventh transistor is shorter than the channellength of the first transistor, and (ii) the resistance value of thefirst transistor is lower than the resistance value of the seventhtransistor in operation.
 21. The signal transmission circuit accordingto claim 18, wherein the power source is commonly connected to said allsignal transmission circuits, said power source being connected to (i)the drain of the first transistor, (ii) the drain and the gate of thefifth transistor, and (iii) the drain of the sixth transistor.
 22. Thesignal transmission circuit according to claim 18, wherein the node iscommonly connected to said all signal transmission circuits, said nodebeing connected to the source of the first transistor and the drain ofthe second transistor.
 23. The signal transmission circuit according toclaim 16, wherein all the transistors are NMOS, and each source of thefirst to third discharging transistor is connected to the earth voltage.24. The signal transmission circuit according to claim 16, wherein allthe transistors are NMOS, and the source of the first error operationpreventative transistor is connected to the earth voltage.
 25. Thesignal transmission circuit according to claim 16, wherein said alltransistors are NMOS, and each source of the first error operationpreventative transistor and the first discharging transistor is providedwith the voltage lower than the threshold voltage of the outputtransistor.
 26. A solid image sensor utilizing a signal transmissioncircuit, wherein the signal transmission circuit includes plural stagesof circuit in each of which the pulse voltage according to the drivingpulse is sequentially outputted, the circuit of each stage including: anoutput transistor outputting the pulse voltage, according to the drivingpulse, to the source; a bootstrap capacitor connected between the gateand the source of the output transistor; a first charging transistorwhose drain is connected to a power source or an earth line and whosesource is connected to the gate of the output transistor in order tocharge the bootstrap capacitor, wherein in the case of the first stage,a start pulse is provided to the gate, and in the case of the secondstage or backward, the gate is connected to the gate of the outputtransistor; a first discharging transistor whose drain is connected toan end of the bootstrap capacitor; a second discharging transistor whosedrain is connected to the other end of the bootstrap capacitor; and anoutput transistor control circuit which prevents the pulse voltage frombeing outputted from the output transistor of each circuit of the otherstages, in the case the pulse voltage is outputted from the source ofthe output transistor.
 27. An Liquid Crystal Display (LCD) apparatusutilizing a signal transmission circuit, wherein a signal transmissioncircuit includes plural stages of circuit in each of which the pulsevoltage, according to the driving pulse, is sequentially outputted, thecircuit of each stage including: an output transistor outputting thepulse voltage, according to the driving pulse, to the source; abootstrap capacitor connected between the gate and the source of theoutput transistor; a first charging transistor whose drain is connectedto a power source or an earth line and whose source is connected to thegate of the output transistor in order to charge the bootstrapcapacitor, wherein in the case of the first stage, a start pulse isprovided to the gate, and in the case of the second stage or backward,the gate is connected to the gate of the output transistor; a firstdischarging transistor whose drain is connected to an end of thebootstrap capacitor; a second discharging transistor whose drain isconnected to the other end of the bootstrap capacitor; and an outputtransistor control circuit which prevents the pulse voltage from beingoutputted from the output transistor of each circuit of the otherstages, in the case the pulse voltage is outputted from the source ofthe output transistor.